Phosphoric esters and their use as dispersants

ABSTRACT

The invention relates to phosphoric esters of the general formula I  
                 
 
     and to their use as dispersants for pigments and fillers in aqueous or organic media.

FIELD OF THE INVENTION

[0001] The present invention relates to phosphoric esters

[0002] a) obtainable by reacting an ω-hydroxy-functional oligo- orpoly(alkyl)styrene with an alkylene oxide to give apoly(alkyl)styrene-block(b)-polyalkylene oxide copolymer and thenconverting said copolymer into the corresponding phosphoric esters witha phosphorus compound which forms phosphoric esters, up to 100% of theterminal hydroxyl groups of saidpoly(alkyl)styrene-block(b)-polyalkylene oxide copolymer being reactedto give phosphoric ester groups and the phosphorus atoms, depending onthe chosen stoichiometric proportions, being mono- and/or diesterified,

[0003] or

[0004] b) based on polystyrene oxide-block(b)-polyalkylene oxidecopolymers obtainable starting from a monofunctional starter alcohol bysequential addition of styrene oxide and of an alkylene oxide inaccordance with the desired sequence and chain length of the individualsegments and subsequently by reaction to give the correspondingphosphoric esters, in the manner described in a).

[0005] The invention relates, furthermore, to the preparation of thesephosphoric esters and to their use as dispersants for pigments andfillers.

BACKGROUND OF THE INVENTION

[0006] For the dispersion of fillers and pigments in liquid media it iscommon to operate with the aid of dispersants in order to reduce themechanical shear forces required for effective dispersion of the solidsand at the same time to obtain very high degrees of filling.

[0007] The dispersants support the disruption of agglomerates, wetand/or cover, as surface-active materials, the surface of the particlesto be dispersed, and stabilize the particles against unwantedreagglomeration.

[0008] Dispersants have become indispensable for the preparation, forexample, of highly concentrated color pastes for the paints and coatingsindustry, for the preparation of pigment concentrates (masterbatches)for the coloring of articles made of plastic, and for the processing ofunsaturated polyester resins (UP resins) which comprise large amounts ofcalcium carbonate or aluminum hydroxide (ATH) as fillers.

[0009] The combination of very high degrees of filling in associationwith a very low viscosity is of particular interest for the producersand users of these products on primarily economic grounds. In the caseof the fillers, these commonly constitute the least expensiveformulating component; pigment concentrates are intended by the plasticsprocessor to be used for coloring in very highly concentrated form—thatis, as far as possible without additional carrier materials.

[0010] Phosphoric esters and their use as dispersants are known and canbe found in the prior art. For instance, U.S. Pat. No. 4,720,514describes phosphoric esters of a range of alkylphenol ethoxylates, whichcan be used with advantage to formulate aqueous pigment dispersions.Phosphoric esters for similar use are described in EP-A-0,256,427. U.S.Pat. No. 5,130,463 and U.S. Pat. No. 5,151,218 report phosphoric estersbased on hydroxy-terminated polyaddition products and polycondensationproducts, which are used for the preparation of highly filled polyestermolding compounds, especially for SMC and BMC formulations (SMC=sheetmolding compounds; BMC bulk molding compounds). Bifunctional phosphoricesters prepared by the Mannich-Moedritzer reaction, and their adsorptioncharacteristics on calcium carbonate, are described in J. Appl. Polym.Sci. 65, 2545 (1997).

[0011] The known phosphoric esters, however, have the disadvantage thatin general they are not universally applicable since there is in manycases a lack of adequate compatibility between the dispersing additiveand binder or between the dispersing additive and the surrounding medium(aqueous or solvent-containing formulations). The chemical compositionof the phosphoric esters also has a large part to play: in aqueousformulations it is preferred to use only those phosphoric esters whosemolecule carries no additional hydrolyzable functional groups, such asester or urethane groups. Frequently, high levels of dispersingadditives are required in order to suppress the incidence ofagglomerates; the degrees of filling which can be achieved areunsatisfactorily low, the stability of the dispersions and thus thepermanence of the viscosity is often inadequate, and flocculation andaggregation cannot always be avoided, possibly resulting in visibleseparation and in flow defects and surface defects.

BRIEF SUMMARY OF THE INVENTION

[0012] It is therefore an object of the present invention to overcome alarge number of the above disadvantages and in so doing to achieve notonly the viscosity reduction of highly filled dispersions that isimportant for processability but also improved compatibility with thesurrounding medium.

[0013] This object is surprisingly achieved through the use ofphosphoric esters of amphiphilic block copolymers having thecharacteristic structural feature of a poly(alkyl)styrene segment and/ora polystyrene oxide segment to which a polyalkylene oxide segment isattached.

[0014] The invention accordingly provides phosphoric esters of thegeneral formula I

[0015] x is 1 or 2,

[0016] n is a number from 2 to 18,

[0017] m and

[0018] o are each a number from 2 to 100,

[0019] k is a number from 2 to 4,

[0020] R″ is H or a linear or branched alkyl radical which may ifdesired be substituted by additional functional groups, and

[0021] R′ is an alkyl, alkaryl, alkenyl or sulfopropyl radical.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Preferably R″=H.

[0023] R′ is commonly derived from an alcohol R′OH which functions asthe starter alcohol for the polymerization of the styrene oxide andalkylene oxide.

[0024] Examples of the radicals R′ are the methyl, butyl, stearyl,allyl, hexenyl, nonylphenyl and oleyl radicals.

[0025] Methyl and butyl radicals are preferred for R′.

[0026] Where n=2 the polyether radical contains exclusively ethyleneoxide units. Where n>2, the polyether radical consists of ethylene oxideunits and, proportionally, of oxyalkylene units whose carbon number isbetween 3 and 18. In this case n can adopt the value of a fractionalnumber between 2 and 18. Preferably, the oxyalkylene block consists ofethylene oxide units, with the additional presence if desired ofoxybutylene units in addition to the oxypropylene units. Oxyalkyleneunits having a carbon number of from 4 to 18 are preferred when, inaddition, it is desired for the product to have oleophilic properties.

[0027] The average molecular weight of the phosphoric esters of theinvention lies within the range from 300 to about 15,000 g/mol,preferably from 500 to 5000 g/mol. It can be determined with great easeby the customary methods of polymer analysis, both for the phosphoricesters and for the amphiphilic block copolymers. The ratio of m to o isfrom 1:50 to 50:1, preferably from 1:10 to 10:1 and, with particularpreference, from 1:2 to 10:1.

[0028] Examples of suitable phosphoric esters are:

[0029] Starting materials used to prepare the phosphoric esters of theinvention are, accordingly, amphiphilic block copolymers of the generalstructures

[0030] respectively, where the radicals R″ and R′ and the indices m, k,n and o are as defined above.

[0031] These block copolymers are prepared by reacting the terminalhydroxyl group with a phosphorus compound which forms phosphoric esters,to give the phosphoric esters of the invention.

[0032] Block copolymers of this kind are described, for example, inDE-A-41 34 967. The polystyrene-b-polyalkylene oxide copolymers of typeA-B are prepared by first subjecting styrene to free-radicalpolymerization in the presence of sufficient amounts of an initiator andof an amount, corresponding to the desired chain length, of a chainregulator which carries not only a mercapto group but also anotherfunctional group having an active hydrogen radical, generally a hydroxylgroup, and subjecting the resulting polymer to an addition reaction attemperatures from 20 to 180° C. with alkylene oxide until the desiredmolecular weight in the block B is reached.

[0033] The corresponding polystyrene oxide-b-polyalkylene oxidecopolymers are prepared, starting from the starter alcohol R′OH, bysubjecting the corresponding alkylene oxides to a sequential additionreaction in accordance with the desired sequence and chain length of theindividual segments so as to give a blocklike structure.

[0034] Both synthetic routes lead to amphiphilic block copolymers havinga terminal hydroxyl group, both including, as an additional,characteristic structural element, a hydrophobic segment composed ofaromatic groups. The processes described make it possible in a simplemanner to adapt the chain lengths m and o of the individual segments,the overall molecular weight and the ratio m/o of aromatic tononaromatic segments to the technical requirements of the particularapplication. For instance, products employed for applications in aqueoussystems are preferably those whose polyalkylene oxide segment iscomposed of ethylene oxide units. Conversely, products having arelatively high proportion of styrene units and/or styrene oxide unitshave proven particularly suitable for dispersion processes in a veryhydrophobic environment, such as, for example, paraffin oils, or in apolyolefin melt.

[0035] The reaction to give the phosphoric esters of the invention takesplace by reaction of the terminal hydroxyl groups with a phosphoruscompound which forms phosphoric esters, in a manner known per se.Examples of suitable phosphorus compounds are phosphorus pentoxide,phosphoryl chloride or polyphosphoric acids of the general formulaH_(n+2)P_(n)O_(3n+1). For the preparation of the phosphoric esters it isparticularly preferred to employ a commercially available polyphosphoricacid (Merck) having a content of about 85% P₄O₁₀. The reaction generallytakes place without solvent at temperatures from about 80 to 100° C. Toremove any traces of moisture present it is possible first of all toremove residues of water from the system using an inert solvent, such astoluene or xylene, for example, prior to the reaction with thepolyphosphoric acid. Alternatively, in principle, the reaction can becarried out in the presence of solvents or solvent mixtures. This isalways advantageous when the phosphoric esters of the invention have tobe formulated in inert solvents or solvent mixtures in accordance withtheir subsequent use.

[0036] The extent of esterification of the terminal hydroxyl group ofthe amphiphilic block copolymers which is the target of esterificationin the esterification reaction is preferably from 50 to 100%; withparticular preference, esterification is quantitative. Depending on theamount of phosphorus compound which forms phosphoric esters, employedrelative to the hydroxyl equivalent of the block copolymers, theproducts of the esterification are alternatively preferably monoesters,diesters, or mixtures of monoesters and diesters.

[0037] Depending on the pH of the medium employed, the phosphoric estersof the invention may also be present in partially or fully neutralizedform.

[0038] The dispersants can either be applied directly to the solids thatare to be dispersed or else can be added to the aqueous and/or organicmedium. They can be distributed in pure form or as a masterbatch inrelatively high concentration in an organic medium. It is of course alsopossible to employ the dispersants to be used in accordance with theinvention together with further auxiliaries or dispersants, such as, forexample, with the stearates known as dispersants.

[0039] Appropriate solids are mineral fillers, such as talc, calciumcarbonate, dolomite, mica, wollastonite, kaolin, and mineral flameretardants, such as aluminum hydroxide or magnesium hydroxide. Suitablepigments are carbon black or titanium dioxide, the latter also beingemployable in finely divided form as a UV protectant in cosmeticformulations. Further dispersible solids are chemical blowing agents,such as azodicarbonamide, or mixtures of solid acids and carbonates.

[0040] The dispersants to be used in accordance with the invention canalso be employed for dispersing ceramic materials in organic media, suchas, for example, finely divided alumina, silicon carbide or siliconnitride.

[0041] Suitable organic media include polyethylene, polypropylene,polystyrene, polyamides, polyesters, poly(meth)acrylates, polyvinylchloride, unsaturated polyesters, and liquid paraffins.

[0042] The dispersants of the invention are particularly suitable forenhancing the distribution of finely divided solids in elastomers,thermoplasts, thermosets and polymer blends.

[0043] The phosphoric esters of the invention have proven particularlysuitable as dispersants for the preparation of highly filled SMC and BMCmolding compounds. SMCs (sheet molding compounds) and BMCs (bulk moldingcompounds) consist of unsaturated polyester resins, a thermoplasticcomponent, glass fibers, and fillers. The unsaturated polyester resinand the thermoplastic component (polystyrene is frequently used as thethermoplastic component) are usually dissolved in monomeric styrenewhich, in the course of processing by compression or injection molding,cures and forms a three-dimensional network structure with theunsaturated polyester resin. The addition of glass fibers leads to hightensile strength and rigidity; the fillers guarantee high compressivestrength and are responsible, moreover, for good dimensional stabilityand low thermal expansion.

[0044] With the phosphoric esters of the invention a very low viscosityis achieved even at very high degrees of filling. The formulationsfeature absolute freedom from inhomogeneities and a high level ofstability on storage.

[0045] In addition, the phosphoric esters of the invention can be usedto prepare aqueous pigment pastes. For this purpose, use is made of from0.1 to 200% by weight of the phosphoric esters, preferably from 0.5 to100% by weight (based on the weight of the pigments). In the case of usein accordance with the invention the phosphoric esters can either bemixed beforehand with the pigments to be dispersed or else can bedissolved directly in the aqueous or solvent-containing dispersionmedium prior to or simultaneously with the addition of pigments and anyother solids.

[0046] Examples of pigments which can be mentioned in this context areorganic and inorganic pigments, including carbon blacks.

[0047] As inorganic pigments mention may be made by way of example oftitanium dioxides and iron oxides. Examples of organic pigments whichmay be considered are azo pigments, metal complex pigments,anthraquinonoid pigments, phthalocyanine pigments, polycyclic pigments,especially those of the thioindigo, quinacridone, dioxazine,pyrrolopyrrole, naphthalenetetracarboxylic acid, perylene,iso-amidolin(on)e, flavanthrone, pyranthrone or isoviolanthrone series.With particular preference, the dispersing additives of the inventionare suitable for preparing aqueous carbon black (gas black) pastes.

[0048] Examples of fillers which can be dispersed in aqueous coatingmaterials are those, for example, based on kaolin, talc, othersilicates, chalk, glass fibers, glass beads, or metal powders.

[0049] Suitable coating systems in which the pigment pastes of theinvention can be incorporated are any desired aqueous 1- or 2-componentcoating materials. Examples which may be mentioned are aqueous1-component coating materials, such as those based on alkyd, acrylate,epoxy, polyvinyl acetate, polyester or polyurethane resins, or aqueous2-component coating materials, examples being those based onhydroxyl-containing polyacrylate or polyester resins with melamineresins or, if desired, blocked polyisocyanate resins as crosslinkers.Similarly, polyepoxy systems may also be mentioned.

[0050] In the examples below, the preparation of the compounds to beused in accordance with the invention is described first of all. This isfollowed by performance examples demonstrating the properties of thecompounds to be used in accordance with the invention and, forcomparison, properties obtainable with some prior art products.

[0051] It is obvious and conventional to the skilled worker that theseexamples represent merely a selection of the possibilities which existand are in no way to be regarded as a limitation.

PREPARATION EXAMPLES

[0052] 1) Preparation of polystyrene-b-polyalkylene oxide copolymers (inanalogy to DE-A-41 34 967, not in accordance with the invention) asstarting materials for the preparation of the corresponding phosphoricesters of the invention

[0053] a) Preparation of a polystyrene-b-polyalkylene oxide copolymer(in analogy to DE-A-41 34 967)

[0054] 100 g of xylene are heated to 120° C. under a nitrogen atmospherein a reactor which is fitted with a stirrer. Over the course of 3 hours,while maintaining the temperature of 120° C., a mixture of 1350 g (about13 mol) of styrene, 78.1 g (1 mol) of 2-mercaptoethanol, 4.1 g ofazodiisobutyronitrile and 310 g of xylene is added. After the end of theaddition, reaction continues for about 15 minutes; subsequently, 0.16 gof methylhydroquinone is added.

[0055] Excess monomer, xylene and residues of 2-mercaptoethanol areremoved by distillation in vacuo and the colorless, viscous liquid whichremains is finally diluted with xylene to a solids content of about 80%.

[0056] The molecular weight Mn determined from the hydroxyl number is700 g/mol. The value for the molecular weight as determined by vaporpressure osmometry is 720 g/mol.

[0057] The solution of 700 g (about 1 mol) of the ω-hydroxy-functionalpolystyrene in 175 g of xylene and 35.0 g of potassium methylate (about0.5 mol) are placed in a thoroughly dried stainless steel reactor whichis additionally fitted with a stirrer. Azeotropic distillation is usedto remove both traces of water and methanol together with xylene.Subsequently, a temperature of 80° C. is established and about 2000 g ofethylene oxide (about 45.5 mol) are added with stirring at a rate suchthat the internal reactor temperature does not exceed 85° C. and thepressure does not exceed 6 bar. After all of the ethylene oxide has beenintroduced, the temperature is held at 80° C. until a constant pressureindicates the end of the subsequent reaction. 100 g of water are addedto the resulting product, which is then brought to a pH of from 6 to 7with 30% phosphoric acid. The water is removed by azeotropicdistillation in vacuo, and the salt which precipitates is removed byfiltration.

[0058] The molecular weight determined from the hydroxyl number, at anassumed functionality of 1, is 2650; the gel permeation chromatogramshows only one maximum and gives a value of 3100 for Mn (calibrationagainst PS); a value of 1.14 is obtained for the ratio Mw/Mn.

[0059] b) Preparation of the phosphoric ester

[0060] 2650 g (corresponding to 1 OH equivalent) of the block copolymerare placed in the reactor, about 50 ml of toluene are added, and thisinitial charge is heated to 120° C. A vacuum is applied to remove all ofthe volatile fractions, especially water which may be present in theproduct, from the reaction chamber by distillation. After blanketingwith nitrogen, the temperature of the contents is stabilized at 80° C.and 85 g of liquid polyphosphoric acid (0.25 mol P₄O₁₀; manufacturer:Merck; purity calculated as P₄O10: about 85%) are added.

[0061] After 2 hours the reaction is at an end. The acid number of theresulting material is 41 mg of KOH/g. An aliphatic hydroxyl group can nolonger be detected in the ¹H-NMR spectrum.

[0062] Table 1 shows examples of some phosphoric esters based on somepolystyrene-b-polyalkylene oxide copolymers, as obtained by the abovepreparation process. The table indicates the molecular weights of thepolystyrene segment and the chemical nature and molecular weight of thecorresponding alkylene oxide. TABLE 1 Mn Mn Phosphoric (polystyrene(polyalkylene Alkylene ester segment)¹ oxide segment)¹ oxide 1A  7002000  EO² 2A  700 1000 EO 3A 1000 1000 EO 4A 1000 1000 EO/PO³ (1:1)⁴ 5A1000 4000 EO 6A  400 1000 EO 7A  400 1800 EO

[0063] 2) Preparation of polystyrene oxide-b-polyalkylene oxidecopolymers (not in accordance with the invention) as starting materialsin the preparation of the corresponding phosphoric esters of theinvention

[0064] 128 g (1.72 mol) of butanol and 12.2 g (0.17 mol) of potassiummethylate are placed in a reactor under a nitrogen atmosphere. Aftercareful flushing with ultrapure nitrogen, this initial charge is heatedto 110° C. and 854 g (7.1 mol) of styrene oxide are added over thecourse of one hour. After a further two hours the addition reaction ofthe styrene oxide is at an end, evident from a residual styrene oxidecontent of less than 0.1% (GC). Subsequently, 2847 g (64.6 mol) ofethylene oxide are metered into the reactor at a rate such that theinternal temperature does not exceed 120° C. and the pressure does notexceed 6 bar. After all the ethylene oxide has been introduced, thetemperature is held at 115° C. until a constant manometer pressureindicates the end of the subsequent reaction. Finally, the unreactedmonomers are removed in vacuo at from 80 to 90° C.

[0065] The resulting product is neutralized using phosphoric acid andthe water is removed by distillation, and the resultant potassiumphosphate is removed by filtration together with a filtering aid. Themolecular weight determined from the hydroxyl number (Mn/OH number), atan assumed functionality of 1, is 1950.

[0066] b) Preparation of the phosphoric ester

[0067] The preparation of the phosphoric ester takes place as describedunder 1b).

[0068] Table 2 shows examples of some phosphoric esters based onpolystyrene oxide-b-polyalkylene oxide copolymers, as obtained by theabove preparation process. The table indicates the molecular weights ofthe polystyrene segment and the chemical nature and molecular weight ofthe corresponding alkylene oxide. TABLE 2 Phosphoric Mn (polystyrene Mn(polyalkylene Alkylene ester oxide segment)¹ oxide segment)¹ oxide 1B450 1500 EO²  2B³ 450 1500 EO  3B 630 1100 EO/VO⁴ (3:1)⁵

[0069] Performance Examples

[0070] The effectiveness of the dispersants to be used in accordancewith the invention is examined in accordance with various methods whichdescribe typical applications in the plastics or coatings sector.

[0071] Method 1:

[0072] The fillers (or pigments) are treated with a solution of the testdispersant in toluene. The toluene is then distilled off and thesurface-treated material is dried in vacuo. The solids coated in thisway are ground in an ultracentrifugal mill (screen size 0.5 mm) in eachcase to the same agglomerate size. Subsequently, the ground solids aredispersed in liquid paraffin (30 cP) using a mizer disk first for 2minutes at 2000 rpm and then 3 minutes at 4000 rpm. For the experimentsin accordance with Method 1 calcium carbonate and aluminum hydroxide arecoated, specifically calcium carbonate (CaCO₃) with 2% by weight ofdispersant and aluminum hydroxide (ATH) with 1% by weight of dispersant,

[0073] The viscosities are measured with a Brookfield spindle viscometer(model LVT) at 23° C. and a rotary speed of 30 rpm with spindles of sizeNo. 3 or No. 4. Table 3 indicates the viscosities of the liquid paraffindispersions filled with the corresponding solids. TABLE 3 Level ofPhosphoric ester Filler filling, % Viscosity/mPas — ATH/CaCO₃ 45 n.d. 1ACaCO₃ 55 720 2A CaCO₃ 55 410 3A ATH 65 660 6A CaCO₃ 55 520 Stearic acidCaCO₃ 55 6900  1B CaCO₃ 55 560 3B CaCO₃ 55 820

[0074] Method 2:

[0075] The fillers are added to a defined mixture which comprises notonly the other formulating constituents but also the dispersant, using astirring motor with a dispersing disk (Ø 50 mm) at a speed of rotationof about 1000 (rpm). For the performance experiments, mixtures arechosen comprising

[0076] 60 parts of unsaturated polyester resin (Palapreg P 17-02 orPalapreg P 14-01; manufacturer: BASF)

[0077] 40 parts of thermoplastic component (Palapreg H 814-01:polystyrene, dissolved in styrene, or Palapreg H 850-01: polymethylmethacrylate, dissolved in styrene; manufacturer: BASF)

[0078] 4.5 parts of zinc stearate

[0079] 1.5 parts of t-butyl perbenzoate

[0080] 180 parts of filler (calcium carbonate/Millicarb OG,manufacturer: Omya or aluminum hydroxide/Martinal ON 310; manufacturer:Martinswerke) and

[0081] X parts of phosphoric esters of the invention.

[0082] In this case the viscosities are measured with a Brookfieldspindle viscometer (model DV-I) at 23° C. and a rotary speed of 50 rpmwith a spindle of type RVT-7. The viscosities are measured after astorage period of 10 minutes. Tables 4 to 7 show the viscosities of thevarious formulations, corresponding to the above formulation variants.In all cases the extent of reduction in viscosity obtainable with thedispersants of the invention is significant. TABLE 4 (UP resin: PalapregP 17-02/thermoplastic component: polystyrene/filler:calcium carbonate)Phosphoric ester Amount/X parts Viscosity (mPas) — — 81000 2A 1.8 290003A 1.8 44500 5A 1.8 51500 6A 1.8 21000 7A 0.9 28500 7A 1.8 18000 7A 2.716000 1B 1.8 18500

[0083] TABLE 5 (UP resin: Palapreg P 14-01/thermoplastic component:polystyrene/filler:calcium carbonate) Phosphoric ester Amount/X partsViscosity (mPas) — — 120000  4A 1.8 28500 7A 1.8 21000 7A 2.7 18000 1B1.8 19500 2B 1.8 19000

[0084] TABLE 6 (UP resin: Palapreg P 17-02/thermoplastic component:polystyrene/filler:ATH) Phosphoric ester Amount/X parts Viscosity(mPas/10 rpm) — — 240000  4A 1.8 50500 7A 1.8 33000  7A¹ 5.2 255000  1B2.7 19000 3B 1.8 21000

[0085] TABLE 7 (UP resin: Palapreg P 17-02/thermoplastic component:polymethyl methacrylate/filler:ATH) Phosphoric ester Amount/X partsViscosity (mPas) — — 54000 1A 1.8 30000 7A 1.8 27000 2B 1.8 19000

[0086] Method 3:

[0087] Preparation of pigment pastes

[0088] To prepare the pigment pastes, the dispersing additives aredissolved beforehand 40% strength in water, mixed with water and, ifdesired, with antifoams, and then the pigments are added. The dispersiontakes place following the addition of grinding media (glass beads 2 to 3mm, same volume as the pigment paste) for one (titanium dioxide) or twohours (other pigments) in a Skandex vibrator with air cooling.

[0089] Formulation of the white pastes

[0090] The white pastes are formulated as follows (amounts in % by wt.):

[0091] 16.4 Water

[0092] 12.3 Additive solution, 40% strength

[0093] 1.0 Defoamer (e.g., Tego Foamex 810, Tego Chemie Service GmbH)

[0094] 70.0 Titanium dioxide 2160 (Kronos)

[0095] 0.3 Aerosil A 200 (Degussa)

[0096] Formulation of the black pastes

[0097] The black pastes are formulated as follows (amounts in % by wt.):

[0098] 60.3 Water

[0099] 22.3 (Dispersing) additive solution, 40% strength

[0100] 1.0 Defoamer (e.g., Tego Foamex 810, Tego Chemie Service GmbH)

[0101] 1.4 2-Amino-2-methylpropanol (Angus)

[0102] 15.0 Pigmentary carbon black FW 200 (Degussa)

[0103] Test coating materials

[0104] Transparent stoving enamel based on a modified alkyd resin(amounts in % by wt):

[0105] 70.88 Alkyd resin Resydrol VWA 5477, 40% strength (Hoechst)

[0106] 0.14 Defoamer (e.g. Byk 020, Byk-Chemie)

[0107] 0.68 Thickener Bentone SD 1 (Rheox)

[0108] 8.24 Melamine resin Maprenal MF 900 (Hoechst)

[0109] 0.14 Triethanolamine

[0110] 19.10 Water

[0111] 0.68 Defoamer Additol XW 395 (Hoechst)

[0112] 0.14 Leveling agent Additol XW 329 (Hoechst)

[0113] Introduce item 1 and add the other components with stirring.

[0114] Transparent emulsion varnish

[0115] 97.0 Acrylate dispersion Neocryl XK 90 (Zeneca)

[0116] 3.0 Texanol

[0117] To prepare paints with gray pigmentation, 40.0 g of transparentenamel or varnish, respectively, 14.2 g of white paste and 2.65 g ofblack paste are added, and the mixture is homogenized at 1500 rpm for 5minutes. The samples are knife-coated onto aluminum panels in a wet filmthickness of 100 μm and are either stoved at 150° C. for 15 minutesfollowing a flash-off time of 20 minutes (stoving enamel) or dried atroom temperature (emulsion paint).

[0118] Test of paste stabilities

[0119] To determine the paste stabilities, the achievable initialviscosities and the viscosities after storage at 50° C. for four weeksare determined at two different shear rates (20 1/s and 1000 1/s). Whitepastes Viscosity/ Viscosity/ Viscosity/ Viscosity/ Pas Pas Pas Pas after4 wk after 4 wk immediate immediate 50° C. 50° C. Sample at 20 l/s at1000 l/s at 20 l/s at 1000 l/s 1A 3.0 0.6 3.4 0.7 2A 3.1 0.5 3.3 0.4 3A3.3 0.7 3.5 0.7 4A 3.0 0.5 3.2 0.5 5A 3.6 0.6 3.8 0.7 6A 3.1 0.4 3.2 0.47A 3.3 0.5 3.4 0.6 1B 3.6 0.5 3.8 0.5 2B 3.5 0.6 3.6 0.6 3B 3.4 0.4 3.30.5 Polystyrene-b- 3.3 0.4 3.7 0.4 polyalkylene oxide copolymerprecursor to 1A Polystyrene-b- 3.5 0.6 3.8 0.7 polyalkylene oxidecopolymer precursor to 3A Fatty acid 2.8 0.5 5.5 1.0 alkoxylate Modified4.2 1.3 6.8 1.5 acrylate polymer

[0120] The good stability of the pigment pastes of the invention isreadily evident from the rise in viscosity, which is small in each case.

[0121] Test of dispersing properties

[0122] Application of the test formulations in a wet film thickness of100 μm; drying for 6 minutes, then rubout test over ⅓ of the surface;after stoving or overnight drying, calorimetric determination of thefilms by means of a XP 68 spectrophotometer from X-Rite; determinationof the degree of gloss and the haze by means of Haze-Gloss fromByk-Gardner. Stoving enamel based on Resydrol VWA 5477 Lightness Delta Eafter Degree of gloss Sample L rubout (60° angle) 1A 41.5 0.4 53 2A 42.30.3 51 3A 41.8 0.4 55 4A 43.2 0.4 53 5A 41.7 0.3 55 6A 40.9 0.5 54 7A41.2 0.3 56 1B 42.2 0.3 54 2B 43.0 0.4 53 3B 42.8 0.3 53Polystyrene-b-polyalkylene 44.0 0.6 51 oxide copolymer precursor to 1APolystyrene-b-polyalkylene 44.2 0.5 52 oxide copolymer precursor to 3AFatty acid alkoxylate 44.6 0.7 49 Modified acrylate 44.9 0.4 55 polymer

[0123] The favorable development of color strength achievable throughthe use of the dispersing additives of the invention, and the rubouttest, which is favorable in all cases, are evident.

[0124] This also becomes particularly marked in comparison with thecommercial examples not in accordance with the invention: a fatty acidalkoxylate (Tego dispers 740W, Tego Chemie Service) and a modifiedacrylate (Tego Dispers 745W).

What is claimed is:
 1. A phosphoric ester of the general formula I

x is 1 or 2, n is a number from 2 to 18, m and o are each a number from2 to 100, k is a number from 2 to 4, R″ is H or a linear or branchedalkyl radical which may if desired be substituted by additionalfunctional groups, and R′ is an alkyl, alkaryl, alkenyl or sulfopropylradical.
 2. A phosphoric ester as claimed in claim 1 , wherein the ratiom/o is from 1:10 to 10:1.
 3. A phosphoric ester as claimed in claim 1 ,wherein the ratio m/o is from 1:2 to 10:1.
 4. A phosphoric ester asclaimed in claim 1 , wherein the average molecular weight is from 300 to15,000 g/mol.
 5. A phosphoric ester as claimed in claim 1 , wherein theaverage molecular weight is from 500 to 5000 g/mol.
 6. A phosphoricester as claimed in any one of claims 1 to 5 , wherein R″=H.
 7. Aprocess for preparing a phosphoric ester as claimed in any one of claims1 to 5 , comprising a) reacting an ω-hydroxy-functional oligo- orpoly(alkyl)styrene with an alkylene oxide to give apoly(alkyl)styrene-block(b)-polyalkylene oxide copolymer and thenconverting said copolymer into the corresponding phosphoric ester with aphosphorus compound which forms phosphoric esters, up to 100% of theterminal hydroxyl groups of saidpoly(alkyl)styrene-block(b)-polyalkylene oxide copolymer being reactedto give phosphoric ester groups and the phosphorus atoms, depending onthe chosen stoichiometric proportions, being mono- and/or diesterified,or b) reacting polystyrene oxide-block(b)-polyalkylene oxide copolymersobtainable starting from a monofunctional starter alcohol by sequentialaddition of styrene oxide and of an alkylene oxide in accordance withthe desired sequence and chain length of the individual segments with aphosphorous compound which forms phosphoric esters, in the mannerdescribed in a).
 8. A process according to claim 7 wherein R″=H.
 9. Themethod of forming a dispersion, comprising dispersing a phosphoric esteras claimed in any one of claims 1 to 5 and one or more pigments orfillers in an aqueous or organic medium.
 10. The method of claim 9wherein R″=H.
 11. The method of forming a highly filled sheet moldingcompound or bulk molding compound, comprising dispersing the componentsof said molding compound and a phosphoric ester as claimed in any one ofclaims 1 to 5 .
 12. The method of claim 11 wherein R″=H.
 13. A pigmentpreparation comprising one or more organic or inorganic pigments andfrom 1 to 100% by weight, based on the pigments, of a dispersingadditive as set forth in any one of claims 1 to 5 .
 14. A pigmentpreparation according to claim 13 wherein R″=H.
 15. An aqueous pastecomprising one or more organic or inorganic colorants and from 1 to 100%by weight, based on the colorants, of a dispersing additive as set forthin any one of claims 1 to 5 .
 16. An aqueous paste according to claim 15wherein R″=H.
 17. A carbon black paste comprising from 10 to 100% byweight of a dispersing additive as set forth in any one of claims 1 to
 5. 18. A carbon black paste according to claim 17 wherein R″=H.